is to mix it with the green sulfate of iron, or the nitrate or muriate of tin: one part of indigo is rendered slowly soluble in warm water by the addition of two of the sulfate of iron and two of lime; part of the lime setting the protoxyd of iron at liberty to deoxygenize the indigo, which is then dissolved, with the assistance of the remainder of the lime, to which a little potash is sometimes added. In calico printing, the indigo is ground with the sulfate of iron and applied to the calico, together with a proper thickening of starch or gum, by means of blocks formed according to the pattern required; the calico is then immersed alternately in lime water and in a solution of the sulfate of iron, until the indigo is become sufficiently dissolved to afford a fixed colour. In this topical application of indigo, red orpiment is sometimes substituted for the sulfate of iron; and Dr. Bancroft has found that sugar is capable of producing a similar effect.

It is well known that indigo may be dissolved in the sulfurie acid without changing its colour; the blues dyed with this solution are called Saxon blues; they are less permanent than those which are derived from the green liquor; and the indigo is deprived of the property of burning with a purple smoke.

The gardenia genipa is mentioned as a plant affording a very permanent bluish black, which might be advantageously employed either for dyeing or as an ink, in countries which allow it to be obtained in a recent state.

The fine rose colour of safflower, extracted by crystallized soda, and precipitated by citric acid, and then slowly dried in the shade, being afterwards finely ground with the purest talc, produces the beautiful paint by which ladies give to their cheeks the bloom of youth and health, and which the French distinguish from carmine by the name of Touge végétale.'

The colouring matter thus derived from the carthamus possesses but little durability; it affords a striking illustration of the Newtonian doctrine of transmitted and reflected colours in the form in which it is sold as a pink dye spread out on saucers. The talc' employed for making rouge is generally that which is now called French chalk, but which will not, like the true French chalk, extract spots of grease.

The finest substantive purples are obtained from lichens. Many species of this genus are employed, after maceration with animal substances containing ammonia, for violet, purple, and crimson dyes: the lichen roccella, or orchil, is the principal; the lichen tartareus is also used in this country, under the name cudbear, given it by Dr. Cuthbert Gordon, who introduced it. After fermentation the substance is kept moist in casks for a year or two

before it comes to perfection; the colours which it affords are however unfortunately fugitive.

The purple obtained from gold, by means of tin, is found to depend on the deoxygenization of the gold by the solution of tin; a similar effect may be obtained by impregnating silk or cotton with glue, eggs, or other animal substances, together with sugar or orpiment, and applying to them the solution of gold. The mi tromuriate of platina affords, in combination with a muriatic solution of tin, a fixed colour like that of arterial blood.

Respecting the antiquity of calico printing, Dr. Bancroft observes, (p. 346,) that Pliny describes the Egyptians as practising a species of topical dying, or calico printing, which, as far as can be discovered from his general terms, appears to have been similar to that which many ages after, was found to exist in Hindostan, and other parts of India, and was from thence introduced into this and other countries of Europe. He says the Egyptians began by painting or drawing on white cloths, (doubtless linen or cotton,) with certain drugs, which in thems selves possessed no colour, but had the property of attracting or ab sorbing colouring matters. After which these cloths were immersed in a beated dying liquor, and though they were colourless before, and though this dying liquor was of one uniform colour, yet, when taken out of it soon after, they were found to be wonderfully tinged of different colours, according to the different natures of the several drugs which had been applied to their different parts; and that these lours, so wonderfully produced from a tincture of only one colour, could not be afterwards discharged by washing."

co

The art of calico printing has been much improved and simplified in modern times, especially by the mixture of the acetate of lead with the aluminous mordant, forming an acetate of alumine. A still more economical method, lately invented, is to employ the acetic acid in the form of the pyrolignic, obtained by the destructive distillation of wood, and to substitute lime for lead. The acetate of iron is also now generally prepared from the pyrolignio acid. MM .Thenard and Roard found that the acetate of alumine, when exposed to a warm atmosphere, lost some of its acid, leaving an excess of alumine; but alum, tartar, and the salts of tin are attached to the fibres of the cloths impregnated with them in their entire state, and may be recovered by repeated washings, until they are decomposed by the operation of the colouring substances. The method of employing some of these substances may be understood from the following description of the proces

ses.

When pieces of calico have been printed with iron liquor, whether it be applied to those which either have received, or are intended to receive, the aluminous mordant also, they are to be thoroughly dried by a stove heat, and afterwards passed through the mixture of cow dung and warm water,' which is supposed not only to cleanse them

more effectually, but possibly to communicate to them some animal impregnation subservient to the durability of the colours; they are afterwards, in the language of t of the c calico printers, to be streamed, or extended in running water, and beat, to remove all the loose or uncombined particles of the mordant, and thus fit them to be dyed with either madder, sumach, weld, or quercitron bark; these being the principal and almost the only adjective colouring matters so employed by calico printers, and sufficient (excepting the blue from indigo) to produce, with the aluminous and ferruginous mordants, all the various colours seen and admired d on printed calico.

Ex. Gr. If pieces of calico, to which these mordants have been applied, both separately and mixed, be put into a dying vessel, with water scarcely blood warm, and in which three, four, or five pounds of madder in powder for each piece have been previously mixed, and they be turned as usual, through the liquor by the winch, gradually, but slowly, raising the heat, so that it may only reach the boiling point at the time when the calicoes will have been sufficiently dyed, the several pieces will be found to have imbibed colour in every part. The figures or places to which the unmixed iron liquor was applied will have been dyed black, and those on which the aluminous mordant was printed will be red, of different shades, if the mordant had been used at different degrees of concentration: and, if both mordants were mixed and applied in different proportions, such applications will have produced various shades of purple, violet, chocolate, and lilac colours, whilst the parts, or grounds intended to be ultimately left white, will manifest a considerable brownnish red discolouration; but as the madder colour producing it is not [there] united to the calico, by the affinity or attraction of any intermediate basis, it will not be able, as in other parts, to resist the action of exterior agents, and may therefore (as is usually done) be removed, and the grounds made white by boiling the pieces in water soured by fermented bran, and by afterwards spreading them for some days(according to the season) upon the grass, where, with the well known treatment, the colours dyed upon a basis will become brighter, whilst that without one will completely disappear.

Calico printed with the same mordants, and dyed with the quercitron bark, (quercus nigra, Linn.) will acquire fixed and bright yellows of different shades, upon the aluminous bases, and various drab colours upon that of iron. A mixture of these bases will produce olive colours. Along with these it is usual to produce black impressions at the same time by previously applying to the calico a mordant composed of iron liquor and galls, by which figures which, without the galls, would only have manifested a dark drab colour, are made black by dying with the quercitron bark, and if the dying be conducted as I shall hereafter direct, the grounds will be so little discoloured that no exposure upon the grass will be required as is necessary with madder and weld, an advantage which has nearly put an end to the use of weld in calico printing. -p. 377.25

The colouring matter of kermes, derived from the coccus ilicis, our author considers as identical with that of cochineal, although VOL. XI. NO. XXI. Tas luban 0.

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combined with some of the astringent substances derived from the tree. The scarlet afforded by cochineal was unknown in its highest perfection till the year 1630, when the singular power of the oxyd of tin, in exalting its colours, was discovered in Holland: it was soon after communicated to one of the celebrated MM. Gobelins at Paris, and contributed to the perfection of the colours of their tapestries. The nitrate or nitromuriate of tin, commonly used by the dyers, affords a crimson colour, which is converted to scarlet by the tartar employed in the process. Dr. Bancroft has invented an ingenious method of saving this valuable colour, by substituting a yellow dye, in particular the quercitron bark, for the acid substance which changes the colour of the cochineal, and thus forming a compound instead of a simple scarlet. The colour thus obtained is more durable than the common scarlet, but, as it is said, not quite so brilliant by day-light, although somewhat brighter by candle-light. The solution of tin, called spirit by the dyers, is usually made with one pound of aqua fortis, two ounces of sea salt or sal ammoniac, half a pound of water, and two ounces of grained tin, added by degrees. Dr. Bancroft attempted to substitute for it a muriate of tin, but found the corrosive quality of this combination extremely injurious to the cloth: he however succeeded much better with a muriosulfate.

Th

process employed in dyeing scarlet on wool requires a mixture of all the materials concerned, before their application to the cloth to apply them in succession, as is either indispensable or highly advantageous in many other cases, would here be impracticable: a fact which renders it necessary to be very cautious in all theoretical reasonings respecting the use of mordants. With silk and cotton, the reverse is true, at least with respect to all dyes except the quercitron.

Since the preparation or manufacture of Morocco leather has been established in this country, cochineal is employed to communicate the beautiful colour of that, which is called red Morocco; though in Persia, Armenia, Barbary, and the Greek islands, a similar colour was originally produced by the use of either kermes or lac. As a basis for the colouring matter of cochineal, goat skins, deprived of their hair by lime water, and properly cleansed, are impregnated, on that which was the hairy side, with a saturated solution of alum, applied repeatedly and equally by a sponge, and, after an interval of three or four days, decoction of cochineal, which has been strained, is applied also by a sponge, to the same side or surface, a little, but not much, more than blood warm, lest it should crisp the leather. This application is repeated from time to time, until a colour sufficiently full and equal has been produced. Afterwards the skins are soaked in bran liquor, and then tanned by a decoction of either galls or sumach, or of both mixed together. I have fo found that by substituting a diluted muriosulfate of tin, for

a

the solution of alum, or by employing a mixture of both upon goat skins in a suitable state of preparation, the colour subsequently produced was considerably improved, at least in vivacity. II. 167.

Dr. Bancroft appears to have bestowed considerable labour and ingenuity on an attempt to obtain the colouring matter of stick lac in a state of purity, and separate from the resin: but it seems to be extremely difficult to exhibit it in an extractive form, without impairing the beauty of the colour. The separation may be part ly effected by employing water not hotter than 190°, which dis solves the colouring matter, and leaves the resin, with some other impurities undissolved; and in this state the colour is as fine as that of cochineal, and somewhat more durable; but it loses its brilliancy in the process of evaporation. The finest parts are also more easily powdered than the rest, and will pass through a sieve while a great portion of the impurities remains behind.

The peculiar colouring matter of Prussian blue, which Dr. Ban croft cannot readily allow to be an acid, as it has usually been de nominated by chemists, affords, with the quercitron bark, a fine green, and as our author first discovered, a good brown with copper. In order to investigate the nature of the green thus obtain ed, he took a piece of cotton which had been printed in stripes with iron liquor and galls, with iron liquor only, with iron liquor and acetate of alumine, and with this acetate only: he dyed it first with quercitron bark, which made the first stripe black, the se cond dark drab, the third olive, and the fourth yellow: he then took prussiated potass, acidulated with sulfuric acid, and immersing the cotton in it for a minute, he found the colouring matter of the galls and quercitron bark discharged where the basis of iron had been employed: so that the first stripe was become a dark blue, and the rest paler, as they stood in order: when there was less excess of acid, the colouring matter of the galls remained, and that of the bark only was discharged: when the liquor was per fectly neutral, the colour of the quercitron bark was discharged from the ferruginous basis, but not from the aluminous; so that the second stripe, with iron liquor, had become blue, and the third a fine green, while the yellow remained perfect on the fourth, and the part not printed became white, being freed from the discoloration of the bark. In these cases of change of colour, the dis placement of one of the substances by the other is sufficiently proved by the state of the liquor, in which the substance displaced is found dissolved.

Among the vegetable adjective colours, weld, the reseda luteola, holds the first place, as having been the longest in use: besides this, young fustic, the rhus cotinus, sumach, the rhus coriaria, old fustic, the morus tinctoria, and French berries, the rhamnus tinctoria, are the most generally known of the yellow dyes. But all